chore: integrate podtemplate/details endpoint into frontend

[andyatmiami]

Migrate the workspace details drawer to fetch volumes, labels, and annotations from the dedicated GET /workspaces/{ns}/{name}/podtemplate/details endpoint (PR #1119) instead of reading them from the list-item payload. This prepares the frontend for PR #1253, which removes pendingRestart, podTemplate.podMetadata, and podTemplate.volumes from the list response.

New hook — useWorkspaceDetails:

• Follows the established useFetchState pattern (useCallback → useFetchState)
• Fetches DetailsWorkspaceDetails on-demand when a workspace is selected
• Returns [data, loaded, error, refresh] matching the standard tuple

Overview tab — labels from details endpoint:

• WorkspaceDetailsOverview now receives details/detailsLoaded props
• Labels read from details?.podMetadata.labels instead of the list item
• Shows a Spinner while the details request is in-flight

Resources tab — volumes from details endpoint:

• WorkspaceResources now receives details/detailsLoaded props
• Home volume and data volumes read from details?.volumes instead of the list item, with Spinner placeholders during loading

Activity tab — pendingRestart computed from redirect chains:

• Removes direct use of workspace.pendingRestart (will be dropped by feat: slim down GET /workspaces payload and remove unused types #1253)
• Derives the same boolean from redirectChain length on podConfig and imageConfig, which is semantically equivalent

Start/Stop modals — drop pendingRestart guard:

• workspacePendingUpdate condition simplified from workspace?.pendingRestart && (redirectChain checks) to !!workspace && (redirectChain checks)
• The !!workspace guard provides explicit null narrowing for TypeScript

Mock builders — backward-compatible refactoring:

• buildMockWorkspaceUpdateFromWorkspace accepts optional podMetadata and volumes args, falling back to list-item fields when not provided, so existing callers are unaffected
• New buildMockWorkspaceDetails builder for the details endpoint response
• mockNotebookApis details mock derives data from the workspace list item for consistency with other mock endpoints

Cypress tests — details endpoint intercepts:

• Add interceptApi type overload for the podtemplate/details route
• Add details endpoint intercepts in setupWorkspaceActionTest and the multi-workspace drawer switching test to prevent unhandled requests

[google-oss-prow]

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